In an effort to delineate the mechanisms that cause the formation of inclusions and induce dopamine cell death in PD, we propose to examine a novel protein, RING-Finger Protein 11 (RNF11) and its interactions with environmental toxins associated with PD pathogenesis. Aim 1: To test that (a) RNF11 is an E3 ubiquitin ligase and (b) that RNF11 is a membrane-associated protein expressed in dopaminergic neurons. Rationale: The RING-domain is essential for recognition of E2 ubiquitin-conjugating enzyme and ubiquitination of spec- ific substrates. Expression of RNF11 in dopaminergic neurons will be suggestive of its site of E3 ubiquitin ligase activity and its role in PD. Approach: We will examine the autoubiquitination properties of RNF11, and its interaction with other proteins using GST pull down assays to determine its substrate/s in cultured cells. We will examine regional, cellular and subcellular distribution of RNF11 in normal rat and human brain by using (a) immunocytochemistry at light and electron microscope levels and (b) sub-cellular fractionation protocols to determine its site of activity. Aim 2: To test the hypothesis that RNF11 has a neuroprotective function and oxidative modification(s) of RNF11 as a result of exposure to environmental toxins will compromise its neuroprotective function. Rationale: As a component of the proteasomal degradation pathway, RNF11 will facilitate or promote clearance of proteins and increase cell viability. Exposure to environmental toxins and oxidative modifications of RNF11 could impair RNF11's role as a neuroprotectant. Approach: In cell culture systems we will examine (A) the role of RNF11 on proteasomal activity and cell survival following (i) exposure to oxidizing agents and (ii) genetic alterations including mutant RNF11 (B) Effects of structural modifications of RNF11 's subcellular distribution and E3 ligase activity and on cell viability. Aim 3: To test the hypothesis that neuroprotective function of RNF11 is compromised in PD due to depletion of functional RNF11. Rationale: Modifications of RNF11 or sequestration of RNF11 in cytoplasmic inclusions will reduce the levels of functional RNF11 and compromise its neuroprotective function. Approach: We will examine changes in RNF11 in (a) animal models of PD ie., rotenone model in rats and a-synuclein transgenic mice and (b) in autopsy brain tissue from PD patients. This study will determine a role for RNF11 and how it confers protection against dopamine cell death seen in Parkinson's disease.